The present invention relates to a downhole tool which is actuatable between at least two tool configurations. In particular, but not exclusively, the present invention relates to a downhole tool comprising a bypass tool for location in a borehole of a well, wherein the bypass tool is actuatable between a closed configuration and an open configuration in response to the flow of fluid through the borehole.
Bypass tools are typically disposed within a borehole of, for example, an oil well, for selectively allowing fluid communication between a bore defined by a tubular string disposed in the borehole, and an annulus defined between an outer wall of the tubing string and an inner wall of the borehole. Typical known assemblies are often complex, comprising many interconnected components, and often require, for example, multiple fluid pressure cycles of fluid in the borehole to actuate the bypass tool between two or more distinct tool configurations.
It is amongst the objects of the present invention to obviate or mitigate at least one of the foregoing disadvantages.
According to the present invention there is provided a fluid flow actuated downhole tool being configurable in at least a first tool configuration and a second tool configuration, the tool comprising:
a tubular housing;
an activating sleeve, the housing being adapted to catch the sleeve when dropped from surface and then permitting actuation of the tool between the first and second tool configurations; and
flow restriction means for permitting fluid flow actuation of the tool when the activating sleeve has been caught in the body.
The invention also relates to a method of operating a fluid flow actuated tool, the method comprising:
running the tool into a borehole in a tubular string;
circulating fluid through the string and the tool;
passing an activating sleeve into the string;
catching the sleeve in the tool; and
circulating fluid through the string, the sleeve and a flow restriction in the tool in order to actuate the tool.
Thus, prior to the sleeve being caught in the tool, the tool is xe2x80x9cdormantxe2x80x9d, and may only be actuated after the sleeve is received in the tool.
As noted above the sleeve is simply dropped into the string and is allowed to fall through the string, or may in addition also be carried into the string by circulating fluid.
Unlike a ball or other flow occluding tool activating member, which will substantially occlude the string bore, the use of a tool activating sleeve allows fluid to continue to flow through the string and tool, and may permit access to the section of the bore below the tool. Also, the use of a sleeve allows fluid to be circulated while the sleeve is moving down through the string; unlike a ball or other flow-occluding device, the sleeve will not induce a large hydraulic shock on engaging the tool.
The sleeve may define a flow restriction, such as a nozzle, which flow restriction permits or facilitates fluid actuation of the tool. Alternatively, the restriction may be defined by another part of the tool, which part is fixed before the sleeve is caught in the tool. Two or more axially spaced flow restrictions may be provided, allowing creation of a greater fluid pressure force without a significant restriction in bore diameter.
The tool may be a bypass tool, preferably the tool being initially closed, and after the sleeve is caught in the tool the tool may be re-configured to permit flow between the tool bore and the surrounding annulus.
Preferably, following activation of the tool by the sleeve, the tool may be repeatedly actuated between the first and second configurations.
A further aspect of the invention relates to a method of operating a fluid flow actuated tool, the method comprising:
(a) running the tool into a borehole in or as a part of a tubular string;
(b) circulating fluid through the string and tool;
(c) passing an activating device into the tool;
(d) catching the device in the tool;
(e) circulating fluid through the string and the tool including the device, to actuate the tool; and
(f) repeating step (e) at least once.
Preferably, the activating device is a sleeve, which may define a restriction or nozzle, incorporate a rupture disc, or contain an extrudable or soluble material.
The activation for the tool may be achieved by releasing a coupling to permit relative movement of parts of the tool, which coupling may be, for example, a shear coupling or a sprung coupling.
Another aspect of the invention relates to a method of actuating a downhole tool, the method comprising:
running a tool into a borehole in a tubular string;
circulating fluid through the string and tool;
locating an activating device in the string; and
circulating fluid through the string and tool as the device travels down through. the string, as the device engages the tool, and following engagement of the device and the tool.
This method is particularly useful in drilling or circulating operations, as there is no requirement to stop fluid circulation as the device moves through the string and then engages the tool, such that drilling or circulation may continue with the device in the string with a fluid flowrate sufficient to entrain drill cutting and carry them to surface, or to allow continuation of some other fluid circulation-related activity. This contrasts with conventional methods, in which it is necessary to stop or at least substantially reduce circulation to prevent the occurrence of a hydraulic shock on the activating device, typically in the form of a steel ball, engaging the tool. Such a hydraulic shock would result in damage to the ball and tool, and possibly also to the string itself.
The activating device may be a sleeve, such that the device restricts fluid flow to a limited extent but does not occlude the string bore.
A still further aspect of the present invention provides a downhole tool for disposition in a borehole of a well, the tool being configurable in at least a first and a second tool configuration, the tool comprising:
a tubular housing for running into a borehole on a tubing string;
a tubular sleeve assembly for disposition within the tubular housing and axially movable therein and including fluid responsive means for actuating the tool between said first and second tool configurations; and
means for maintaining said sleeve assembly in a selected one of said first and second tool configurations.
Thus the present invention allows a downhole tool to be disposed in a borehole, which tool may be actuated between two or more tool configurations by supplying fluid to the tool in the borehole and by varying the flow rate of the fluid through the tool.
Preferably, the downhole tool is a bypass tool. The bypass tool may be in a closed configuration in the first tool configuration and an open configuration in the second tool configuration. The tubular housing may form part of a liner, casing, or drill string or any other tubing string for disposition in the borehole.
The tubular housing of the bypass tool may comprise at least one bypass port extending through a wall of the housing. The at least one bypass port may extend radially through the wall of the housing. The sleeve assembly may be axially movable to selectively move to the open configuration, to allow fluid communication between the housing interior wall, and an annulus defined by an outer face of the housing wall and the borehole wall.
The fluid responsive means may include a flow restriction, such that flow of fluid induces a pressure differential, and therefore a fluid pressure force, across the restriction. Alternatively, said means may define a differential piston with, for example, one piston face experiencing internal housing pressure and another face experiencing annulus pressure, such that an increase in internal pressure will actuate the tool.
The tubular sleeve assembly may comprise a control sleeve and a flow restriction within the control sleeve for restricting the flow of fluid through the control sleeve.
Preferably, the restriction is defined by an insert which may be dropped or lowered from the surface into the tubing string and may travel through the string and engage the control sleeve. Fluid flow through the flow restriction creates a force acting axially across the flow restriction, and thus on the control sleeve, urging the sleeve assembly to move axially. Alternatively, the flow restriction may be integral with the control sleeve. The flow restriction may comprise an annular, radially inwardly extending ring defining a nozzle.
The maintaining means may comprise a releasable connection, such as one or more sprung dogs, keys or a shear connection, such as one or more shear pins, for engaging the control sleeve and maintaining it in a selected one of said first and second tool configurations.
The bypass tool may further comprise a flow restriction-engaging insert, such as a nozzle, dart, sleeve or ball, for engaging the flow restriction, although as noted above in other embodiments the insert may itself provide the flow restriction. Thus, in response to pressurisation of the fluid in the tubing string above the insert, a pressure force acting across the insert may be caused to urge the tubular sleeve assembly axially downwardly to release the connection, and in addition or alternatively to actuate the tool. The flow restriction engaging insert may be injected into the tubing string at the surface and may travel through the string bore to engage the flow restriction. When the insert is a ball, preferably the ball is deformable to allow the ball to be forced through the flow restriction in response to an increase in the pressure of the fluid in the tubing string above the ball.
In an alternative arrangement, the tubular insert may be adapted to release the connection on engaging the control sleeve.
Preferably, the downhole tool further comprises indexing means for selectively allowing actuation of the tool between said first and second tool configurations. The indexing means may comprise a cam arrangement such as a groove, slot or other profile extending around an outer circumference of the tubular sleeve assembly, and a cam follower such as a pin extending radially inwardly from an inner surface of the housing for engaging the groove. of course, in alternative arrangements the groove or the like may be defined by the housing, and the pin or the like mounted on the sleeve assembly. In still further arrangements, the indexing means may be provided between different parts of the sleeve assembly. The pin and groove may co-operate to rotate the tubular sleeve assembly, or at least a part of the assembly, when it is moved axially. Conveniently, the groove defines first and second axial pin rest positions. Preferably, the groove defines a plurality of first and second axial pin rest positions. The first axial pin rest position may correspond to a valve open configuration and the second axial pin rest position may correspond to a valve closed configuration. The groove may further define a plurality of third axial pin rest positions for allowing actuation of the tool to an intermediate configuration between said first and second tool configurations, and which intermediate position may provide a further tool function, or may correspond to the function provided by one of the first or second tool configurations. The third axial pin rest positions may be provided between second axial pin rest positions. Thus the groove and pin may allow the tool to be disposed in the intermediate configuration alternatively when the pressure in the borehole is increased.
The maintaining means may further or alternatively comprise a spring for applying a force upon the sleeve assembly. The spring may be a fluid spring or a compression or tension spring. Preferably, the spring is disposed in an annular cavity between the housing and the sleeve assembly, to impart an upward force upon the sleeve assembly, to maintain it in a closed configuration.